This invention relates particularly to a copying machine wherein copying is effected by subjecting a draft sheet during conveyance to slit exposure.
The copying machine of this sort involves the problems that in case a draft sheet during conveyance skews, a copied image is slant, and much the worse, a copied image breaks off.
In order to prevent such problems from occurring, there is proposed a copying machine equipped with a correction apparatus as disclosed in Japanese Laid Open Patent Application No. 93848/1982. This copying machine employs a skew feed correction apparatus as shown in FIG. 1 and FIG. 2. This apparatus will be explained briefly. When a draft sheet 201 is conveyed in a skewed state as shown in FIG. 1, there is caused a time lag between the draft sheet sensing times by skew sensors 202, 203. If this time lag is more than a predetermined time, in case the sensor 202 has first sensed the draft sheet the sensor 202 actuates a solenoid 204, and contrarily in case the sensor 203 has first sensed the draft sheet the sensor 203 actuates a solenoid 205 respectively for tilting a correction means by .alpha. degree counterclockwise or clockwise with p as a fulcrum. And, skew correction is made when the draft sheet 201 is guided by a curved guide surface 208 of a guide means 207 and turned as shown in FIG. 2.
However, the copying machine of this sort is disadvantageous in that since said turning means is disposed in a convey way for the draft sheet, a convey passage is prolonged thereby to restrict the lay out of the machine. In addition thereto, this copying machine is disadvantageous in that since the correction means tilts by a predetermined degree .alpha. irrespective of many or few of the skewed amount, it leads to insufficient or over correction, and so pertinent correction is difficult; and that since the tilting angle .alpha. of the correction means is constant irrespective of great and small sizes of the draft sheet width, the correction amount of the small-wide draft sheet is less than that of the great-wide draft sheet and consequently it is difficult to do pertinent correction corresponding to the great or small width of the draft sheet and when the skewed amount is over the predetermined amount it is out of correction and so copying is effected using the non-corrected draft sheet so as to result in image-broken useless copies.
Furthermore, in case the length of the draft sheet is long the skew amount corrected by the guide means 207 is increased, and contrarilly in case the length of the draft sheet is short the skew amount to be corrected is decreased. Accordingly, the draft sheet circling type copying machine, wherein a lower convey way and an upper convey way communicating therewith are provided; said upper convey way is provided with plural guide means appearing and disappearing for circling the draft sheet to said lower convey way; one and the same draft sheet is conveyed many times repeatedly between both convey ways by the action of this guide means; and plural copies are generated from one and the same draft sheet, is also disadvantageous in that as the result of plural times of circulation, when the draft sheet is long the skew correction amount per one time is so large that over correction is likely to cause a skew on the opposite side, while when the draft sheet is short the skew correction amount per one time is so small that the skew correction amount increases gradually and ultimately the copied image breaks, whereby useless copies are generated.
Further, said draft sheet circling type copying machine is disadvantageous in that despite the possibility of sideslip of the draft sheet occurring in addition skew thereof, the usual correction apparatus is unable to detect this sideslip and consequently useless copies with broken image are produced.